A tree-ring densitometric transect from Alaska to Labrador

We describe a recently completed network of densitometric tree-ring time series representing various aspects of tree-growth for up to 200 years at 69 sites spread across the northern North American conifer zone from Yukon to Labrador. Duplicate cores, from 12 to 15 trees per site, provide time series for a suite of growth parameters including earlywood (spring), latewood (summer) and total (annual) ring widths and mean earlywood, mean latewood, minimum and maximum ring density. These data form the basis for extensive analyses of intra- and inter-site parameter comparisons and regional climate/tree-growth comparisons. Five large-scale regional chronologies do not suggest that any anomalous growth increases have occurred in recent decades, at least on these regional scales, despite the observed changes in atmospheric composition and climate.     

Population studies on a South African carrageenophyte: Iridaea capensis (Gigartinaceae,Rhodophyta)

An intertidal population of Iridaea capensis in the south-western Cape Province of South Africa has been studied in detail for a year. The species is generally restricted to sand-inundated rocky shores, which appears not to be the case for Iridaea species in the Pacific. In early winter (June) biomass, plant density and plant size were at a minimum. A small increase in these parameters occurred in August, but there was a massive increase in plant numbers and biomass in October. The largest plants were recorded in summer (February). The population was over 70% sporophytes in April, but switched to almost 80% gametophytes following heavy recruitment between August and October, and remained significantly gametophyte-dominated through April of the following year. Carrageenan levels were high (ca 42% of dry weight) in late winter-spring, and lowest (ca 30–35%) in summer-autumn. Strong offshore wind conditions in early summer caused a reduction in biomass, and it is hypothesized that the associated upwelling of nutrient rich water may be implicated in the lower carrageenan levels at this time.     

DISTRIBUTION AND SYSTEMATICS OF FRESHWATER CERAMIALES (RHODOPHYTA) IN NORTH AMERICA1

Twenty-five freshwater populations of Ceramiales were collected in North America, 24 of which were from the tropical rainforest region of Central America and the Caribbean. The streams tended to be moderate in mean current velocity (X?= 23.3 cm·S^?1) and maximum width (X?= 6.3 m) but high in temperature (X?= 23.1°C), pH (X?= 7.9), and specific conductance (X?= 320 μS·cm^?1). Three Bostrychia species were restricted to the Caribbean islands: B. moritziana (Sonder ex Kütz.) J. Ag. (syn. B. cornigera Mont. and B. radicans f. moliforme Post), with ecorticate indeterminate axes, monosiphonous ultimate branches, and cladohaptera; B. radicans (Mont.) Mont. (syn. B. leprieurii Mont and B. rivularis Harv.), with ecorticate and polysiphonous axes throughout and cladophaptera; and B. tenella (Lamour.) J. Ag., with corticate indeterminate axes, monosiphonous ultimate branches, and peripherohaptera. Ballia prieurii Kütz. was found in Belize and Costa Rica and was characterized by rebranched determinate laterals, opposite branching, and long apical cells (X?= 61 μm) and axial cells (X?= 43 μm). Caloglossa leprieurii (Mont.) J. Ag. was localized in Puerto Rico while. C. ogasawaerensis Okam. was collected only in Costa Rica. The two species were separated by site of branching (midrib vs. margin) and blade width (X?= 384 vs. 861 μm). Polysiphonia subtilissima Mont. from Florida and Jamaica had four pericentral cells, no cortication, rhizoids arising from pericentral cells, and branches initiated at trichoblast scars.     

Review of the genus Hippidion Owen, 1869 (Mammalia: Perissodactyla) from the Pleistocene of South America

This review of Hippidion is based on a multivariate analysis of the foot, and some morphological characteristics of the skull and dentition. We recognize only one genus ( Hippidion ) including all the hippidiform horses, with three different species: H. principale, H. devillei and H. saldiasi. The latter species is stratigraphically and geographically restricted to the period from 13000 to 8000 years BP in the southern part of South America. Hippidion principale and H. devillei have a large geographical distribution (Argentina, Bolivia, Chile, Perú, Uruguay, Brazil) through the Upper Pliocene-Upper Pleistocene. Both species show some morphometric variations across their geographic range; these features may result from the environmental characteristics.     

Differences in physical growth of Aymara and Quechua children living at high altitude in Peru

Physical growth of Amerindian children living in two Aymara and three Quechua peasant communities in the Andean highlands of southern Peru (altitude 3,810–3,840 m) was studied, taking into account differences in the microclimate, agronomic situation, and sociodemographic variables. Anthropometric measurements were taken in 395 children aged under 14 years of age in a sample of 151 families in these communities, who were surveyed for sociodemographic variables as well. Data on the land system were available for 77 families. In comparison with reference populations from the United States (NCHS) and The Netherlands, stature, weight, head circumference, and midupper arm circumference (but not weight for stature) in the sample children were reduced. Growth retardation increased after the age of 1 year. Stature and weight in the present sample were very similar compared with previously published data on growth of rural Aymara children living near Lake Titicaca in Bolivia. Head circumference, midupper arm circumference, and weight for stature were significantly larger in Aymara children compared with Quechua children. Land was significantly more fragmented in Aymara compared with Quechua families, but amount of land owned was not different. Perinatal and infant mortality was elevated in Aymara vs. Quechua communities. Most families in Aymara communities used protected drinking water. One Quechua community had a severe microclimate, grim economic outlook, and weak social cohesion. Children in this community showed significant reductions in weight and midupper arm circumference compared with their peers in the other communities. We conclude that (presumably nutritionally mediated) intervillage and Aymara-Quechua differences in childhood physical growth existed in this rural high-altitude population in Peru and were associated with microclimate and the village economy, sociodemographic factors, and differences in the land system. © 1993 Wiley-Liss, Inc.     

Evolution of the Pretoria Saltpan — a diatom record spanning a full glacial-interglacial cycle

Hydrobiologia - In 1988–89 a 200 m core was drilled down to granite bedrock in the Pretoria Saltpan as part of a project to ascertain the origin of this unusual feature. The top 90 m of the...     

Quaternary and recent Lamprothamnium groves (Charophyta) from Argentina

Only recently have extant Lamprothamnium species been reported from the American continent. L. succinctum (A. Br. in Asch.) R. D. W. was found in Lago Titicaca, Bolivia and L. haesseliae Dont. en Laguna Luro and Laguna La Salada, Argentina.Fossil gyrogonites of L. succinctum and L. haesseliae, however, are here reported to be widely distributed in Quaternary sediments of Argentina, associated with other charophytes, ostracods and foraminiferans. Localities include Laguna del Siasgo, Laguna Salada Grande, Laguna Mar Chiquita, Laguna La Amarga and Salina del Bebedero. Lamprothamnium is a genus that prefers shallow, alkaline, hyposaline to mesosaline environments. Analysis of the characteristics of Laguna La Salada contributes information on the factors that influence the distribution of the genus.The morphology characteristics of the gyrogonites and oospores of L. haesseliae and the gyrogonites of L. succinctum are described. The use of Lamprothamnium as a biomarker and its application in the reconstruction of Quaternary saline environments are also discussed.     

Short-term photosynthesis measurements predict leaf carbon balance in tropical rain-forest canopy plants

Diel (24 h) courses of net CO₂ exchange of leaves were determined in eight species of tropical rainforest plants on Barro Colorado Island, Panama, during 1990 and 1991. The species included three canopy trees, one liana, two epiphytes and one hemiepiphyte. One of the species studied was growing in a rain-forest gap. Daily carbon gain varied considerably across species, leaf age, and season. The analysis of data for all plants from 64 complete day/night cycles revealed a linear relationship between the diurnal carbon gain and the maximum rate of net CO₂ uptake, A_max. Nocturnal net carbon loss was about 10% of diurnal carbon gain and was positively related to A_max. We conclude that short-term measurements of light-saturated photosynthesis, performed at periodic intervals throughout the season, allow the annual leaf carbon balance in these rain-forest plants to be predicted.     

Tube-snouted gymnotiform and mormyriform fishes: convergence of a specialized foraging mode in teleosts

Synopsis African mormyriform and South American gynmotiform fishes are unique among freshwater fishes in their abilities to generate and perceive an electrical field that aids in orientation, prey detection, and communication. Here we present evidence from comparative ecology and morphology that tube-snouted electric fishes of the generaSternarchorhynchus (Apteronotidae) andCampylomormyrus (Mormyridae) may be unique among fishes in their mode of foraging by grasp-suction. The grasp-suction mode of feeding is a specialization for extracting immature stages of aquatic insects that burrow into, or hide within, interstitial spaces and holes in matrices of compacted clay particles that form the channel bottom of many tropical lowland rivers. Ecomorphological implications of the remarkable evolutionary convergence for this specialized mode of foraging by tube-snouted electric fishes provide a challenge to Liem's (1984, 1990) theory of separate aquatic and terrestrial vertebrate feeding modes.Invited Editorial